Hello Bjorn,
> From: Bjorn Helgaas, Sent: Thursday, October 19, 2023 12:11 PM
>
> On Wed, Oct 18, 2023 at 05:56:16PM +0900, Yoshihiro Shimoda wrote:
> > Add R-Car S4-8 (R-Car Gen4) PCIe controller for both host and endpoint modes.
> > To support them, modify PCIe DesignWare common codes.
> >
> > Changes from v24:
> >
<snip URL>
> > - Based on the latest pci.git / next branch.
> > - Reordering the patches. (This is suggested by Bjorn.)
> > - Drop "PCI: dwc: Disable two BARs to avoid unnecessary memory assignment"
> > because break other platforms.
>
> Does R-Car Gen4 still work without this patch?
Yes, R-Car Gen4 still work without this patch because I added this code into
the patch 12/15 again:
---
+static int rcar_gen4_pcie_host_init(struct dw_pcie_rp *pp)
+{
...
+ /*
+ * According to the section 3.5.7.2 "RC Mode" in DWC PCIe Dual Mode
+ * Rev.5.20a and 3.5.6.1 "RC mode" in DWC PCIe RC databook v5.20a, we
+ * should disable two BARs to avoid unnecessary memory assignment
+ * during device enumeration.
+ */
+ dw_pcie_writel_dbi2(dw, PCI_BASE_ADDRESS_0, 0x0);
+ dw_pcie_writel_dbi2(dw, PCI_BASE_ADDRESS_1, 0x0);
---
I also mentioned about this on the cover-letter like below, but it may be difficult
to understand. I'm sorry about lack explanation... I should have explained one sentence
about that...
>> - Add specific-setting by using dbi2 again in the patch 12/15.
>> - Modify commend of the specific-setting in the patch 12/15. Serge suggested
>> this on v23 but I missed to modify this on v24.
> The previous commit log said host mode didn't work:
>
> PCI: dwc: Disable two BARs to avoid unnecessary memory assignment
>
> According to the section 3.5.7.2 "RC Mode" in DWC PCIe Dual Mode
> Rev.5.20a, we should disable two BARs to avoid unnecessary memory
> assignment during device enumeration. Otherwise, Renesas R-Car Gen4
> PCIe controllers cannot work correctly in host mode.
>
> (from https://lore.kernel.org/all/20231011071423.249458-9-yoshihiro.shimoda.uh@xxxxxxxxxxx/)
>
> I don't think we want to merge the driver unless it actually works.
I understood it.
Best regards,
Yoshihiro Shimoda
> Bjorn
